A local oscillator generator (LOGEN) circuit is utilized in a conventional transceiver to generate oscillator reference signals. The oscillator reference signals generated by the LOGEN circuit are utilized by a transmitter and/or a receiver. Since different reference frequencies may be utilized for transmitter and/or receiver operations, multiple local oscillator generators are utilized in conventional transceivers. For example, one or more LOGEN circuits may be utilized by a transmitter block and one or more LOGEN circuits may be utilized by a receiver block within a transceiver. For each LOGEN circuit, a conventional transceiver utilizes one or more calibration circuits that calibrate the LOGEN circuit for a specific frequency or a range of frequencies.
The LOGEN circuits within the transmitter and/or receiver block, however, occupy significant on-chip real estate within a conventional transceiver. In addition, additional on-chip real estate is required for the calibration circuits corresponding to each of the LOGEN circuits utilized within the transceiver. Further, by utilizing several LOGEN circuits, there is an increased possibility of inter-oscillator interference, which causes ineffective oscillator signal generation and decreases efficiency.
LOGEN circuits may be adapted to utilize one or more voltage controlled oscillators (VCOs). The VCOs may be adapted to generate one or more differential frequency outputs and may be followed by one or more divider circuits that divide the generated differential frequency outputs. The VCOs, however, are sensitive to loading from following divider circuits and/or other interconnections. For example, large capacitance and/or resistance created by dividers and line routing limit VCO performance. Conventional LOGEN circuits, therefore, utilize buffers to provide the VCO with a known, reasonable load impedance and enough power to drive any dividers and interconnections with the large signal these devices require to operate correctly.
Buffers within conventional LOGEN circuits utilize one or more transistors as transconductors. In addition, resistors are used to isolate buffer inputs and/or outputs, as well as for biasing loading circuits within the buffer. Each of these resistors, however, contribute to an increase in parasitic capacitance and overall excess loading of the buffer outputs. Further, bias setting resistors, as well as direct current (DC) voltage source transistors within the buffer, utilize significant headroom to function properly. Consequently, as supply voltages within integrated circuits containing conventional buffers decrease with improvements in radio signal processing technology, gain and output swing characteristics of the buffer decreases.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of ordinary skill in the art through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.